\nI often see people write code that goes something like this:\n<\/p>\n
\n\/\/ do not use - see discussion\nvoid DoSomethingToWindowTree(HWND hwndRoot)\n{\n \/\/ first do it to the window passed in\n DoSomething(hwndRoot);\n \/\/ now do it to all the children\n EnumChildWindows(hwndRoot, DoSomethingHelper, 0);\n}\nBOOL CALLBACK DoSomethingHelper(HWND hwnd, LPARAM lParam)\n{\n DoSomethingToWindowTree(hwnd);\n return TRUE;\n}\n<\/i><\/pre>\n\nThe intent here was to perform the operation on all the windows\nin a window tree by operating on the root, then operating on\neach of the children.\nOperating on the children is in turn performed recursively,\nso that we eventually see every window in the tree.\n<\/p>\n
\nExcept that if you actually run this function on a vaguely\ninteresting window tree, you’ll find that items get counted\nmultiple times.\n<\/p>\n
\nThe reason is that the EnumChildWindows<\/code> function\nalready does the recursion<\/strong>:\n<\/p>\n\nIf a child window has created child windows of its own,\nEnumChildWindows<\/b> enumerates those windows as well.\n<\/p><\/blockquote>\n
\nIf you add your own recursion, then you end up counting\ngrandchildren twice, great-grandchildren four times, and so on.\nThe recursion is already done by EnumChildWindows<\/code>;\njust use it.\n<\/p>\n\nvoid DoSomethingToWindowTree(HWND hwndRoot)\n{\n \/\/ first do it to the window passed in\n DoSomething(hwndRoot);\n \/\/ now do it to all the descendants (children, grandchildren, etc.)\n EnumChildWindows(hwndRoot, DoSomethingHelper, 0);\n}\nBOOL CALLBACK DoSomethingHelper(HWND hwnd, LPARAM lParam)\n{\n DoSomething(hwnd);\n return TRUE;\n}\n<\/pre>\n","protected":false},"excerpt":{"rendered":"I often see people write code that goes something like this: \/\/ do not use – see discussion void DoSomethingToWindowTree(HWND hwndRoot) { \/\/ first do it to the window passed in DoSomething(hwndRoot); \/\/ now do it to all the children EnumChildWindows(hwndRoot, DoSomethingHelper, 0); } BOOL CALLBACK DoSomethingHelper(HWND hwnd, LPARAM lParam) { DoSomethingToWindowTree(hwnd); return TRUE; } […]<\/p>\n","protected":false},"author":1069,"featured_media":111744,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":""},"categories":[1],"tags":[25],"class_list":["post-28393","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-oldnewthing","tag-code"],"acf":[],"blog_post_summary":"
I often see people write code that goes something like this: \/\/ do not use – see discussion void DoSomethingToWindowTree(HWND hwndRoot) { \/\/ first do it to the window passed in DoSomething(hwndRoot); \/\/ now do it to all the children EnumChildWindows(hwndRoot, DoSomethingHelper, 0); } BOOL CALLBACK DoSomethingHelper(HWND hwnd, LPARAM lParam) { DoSomethingToWindowTree(hwnd); return TRUE; } […]<\/p>\n","_links":{"self":[{"href":"https:\/\/devblogs.microsoft.com\/oldnewthing\/wp-json\/wp\/v2\/posts\/28393","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/devblogs.microsoft.com\/oldnewthing\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/devblogs.microsoft.com\/oldnewthing\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/devblogs.microsoft.com\/oldnewthing\/wp-json\/wp\/v2\/users\/1069"}],"replies":[{"embeddable":true,"href":"https:\/\/devblogs.microsoft.com\/oldnewthing\/wp-json\/wp\/v2\/comments?post=28393"}],"version-history":[{"count":0,"href":"https:\/\/devblogs.microsoft.com\/oldnewthing\/wp-json\/wp\/v2\/posts\/28393\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/devblogs.microsoft.com\/oldnewthing\/wp-json\/wp\/v2\/media\/111744"}],"wp:attachment":[{"href":"https:\/\/devblogs.microsoft.com\/oldnewthing\/wp-json\/wp\/v2\/media?parent=28393"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/devblogs.microsoft.com\/oldnewthing\/wp-json\/wp\/v2\/categories?post=28393"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/devblogs.microsoft.com\/oldnewthing\/wp-json\/wp\/v2\/tags?post=28393"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}